EXHALATION FROM THE SKIN. 437 



with a mouthpiece. The bag being closed by a strong 

 band above, and the mouthpiece adjusted and gummed to 

 the skin around the mouth, he was weighed, and then re- 

 mained quiet for several hours, after which time he was 

 again weighed. The difference in the two weights indi- 

 cated the amount of loss by pulmonary exhalation. Having 

 taken off the air-tight dress, he was immediately weighed 

 again, and a fourth time after a certain interval. The 

 difference between the two weights last ascertained gave 

 the amount of the cutaneous and pulmonary exhalation 

 together ; by subtracting from this the loss by pulmonary 

 exhalation alone, while he was in the air-tight dress, he 

 ascertained the amount of cutaneous transpiration. The 

 repetition of these experiments during a long period, 

 showed that during a state of rest, the average loss by 

 cutaneous and pulmonary exhalation in a minute, is from 

 seventeen to eighteen grains, the minimum eleven grains, 

 the maximum thirty-two grains ; and that of the eighteen 

 grains, eleven pass off by the skin, and seven by the lungs. 

 The maximum loss by exhalation, cutaneous and pulmo- 

 nary, in twenty-four hours, is about 3! Ib. ; the minimum 

 about i^ Ib. Valentin fou-nd the whole quantity lost by 

 exhalation from the cutaneous and respiratory surfaces of 

 a healthy man who consumed daily 40,000 grains of food 

 and drink, to be 19,000 grains, or 2^ Ibs. Subtracting 

 from this, for the pulmonary exhalation, 5,000 grains, 

 and, for the excess of the weight of the exhaled carbonic 

 acid over that of the equal volume of the inspired oxygen, 

 2,256 grains, the remainder, 11,744 grains, or nearly 

 if Ibs., may represent an average amount of cutaneous 

 exhalation in the day. 



The large quantity of watery vapour thus exhaled from 

 the skin, will prove that the amount excreted by simple 

 transudation through the cuticle must be very large, if we 

 may take Krause's estimate of about eight square inches 

 for the total evaporating surface of the sudoriparous 



